Slurry compounds and methods of fabricating semiconductor devices using the same

ABSTRACT

Provided are slurry compounds for polishing an SOH organic layer and methods of fabricating a semiconductor device using the same. The slurry compound may include a polishing particle, an oxidizing agent including at least one selected from the group consisting of a nitrate, a sulfate, a chlorate, a perchlorate, a chlorine, and a peroxide, and a polishing accelerator.

CROSS-REFERENCE TO RELATED APPLICATION

This U.S. non-provisional patent application claims priority under 35U.S.C. §119 to Korean Patent Application No. 10-2014-0159064, filed onNov. 14, 2014. The contents of which are incorporated herein byreference in its entirety.

FIELD

Example embodiments of the inventive concept relate to slurry compoundsand methods of fabricating a semiconductor device using the same, and inparticular, to methods of electrically isolating metal lines from eachother by an air gap using the slurry compounds.

BACKGROUND

At least due to their small-size, multifunctionality, and/or low-costcharacteristics, semiconductor devices are considered important elementsin the electronic industry. The semiconductor devices can be generallyclassified into a memory device for storing data, a logic device forprocessing data, and a hybrid device capable of performing variousfunctions.

There is an increasing demand for a semiconductor device with a higherintegration density and higher performance. Although a variety ofstudies are being conducted to meet such a demand, it is desired toreduce a process margin (for example, in a photolithography process) andthis may lead to several difficulties in fabricating a semiconductordevice.

SUMMARY

Example embodiments of the inventive concept provide a slurry compound,allowing a polishing process to be effectively used in fabrication of ahighly-integrated semiconductor device.

Other example embodiments of the inventive concept provide a method offabricating a highly-integrated semiconductor device.

According to example embodiments of the inventive concept, a slurrycompound for polishing a spin-on-hardmask (SOH) organic layer mayinclude a polishing particle, an oxidizing agent containing at least oneselected from the group consisting of nitrate, sulfate, chlorate,perchlorate, chlorine, and peroxide, and a polishing accelerator.

In example embodiments, the polishing particle may include colloidalceria (CeO₂) particles.

In example embodiments, the polishing particle may have a size rangingfrom about 30 nm to about 80 nm.

In example embodiments, the oxidizing agent may be contained in theslurry compound to have a content ranging from about 0.2 wt % to about0.7 wt % with respect to a total weight of the slurry compound.

In example embodiments, the oxidizing agent may include at least one ofhydrogen peroxide, ammonium perchlorate, sodium chlorate, sodiumchlorite, or ferric nitrate.

In example embodiments, the polishing accelerator may be adsorbed on asurface of a metal to protect the metal against corrosion.

In example embodiments, the polishing accelerator may include at leastone an amino acid selected from the group consisting of histidine,glycine, glutamine, leucine, methionine, phenylalanine, tryptophan, andvaline.

In example embodiments, the polishing accelerator may include at leastone selected from the group consisting of imidazole, imidazolium,chloride, pyridine, tetrazoles, histamine, 1,3-dimethylxanthine,6-mercaptopurine, 1H-1,2,3-triazole, 1H-1,2,4-triazole,poly-[2,2′-(m-phenylen)-5,5′-bisbenzimidazole], 1H-Pyrrole, 1,3-oxazole,1,3-thiazole, Pyrazole, 1-Methylimidazole, and 4-Methyl-1H-imidazole.

According to example embodiments of the inventive concept, a method offabricating a semiconductor device may include forming metal lines on asubstrate, forming an SOH organic layer on the metal lines to fill gapsbetween the metal lines, performing a polishing process on the SOHorganic layer to expose top surfaces of the metal lines and form SOHorganic patterns between the metal lines, forming a thin film on themetal lines and the SOH organic patterns, and selectively removing theSOH organic patterns to form air gaps between the metal lines. Thepolishing process may be performed using a slurry compound including apolishing particle, an oxidizing agent containing at least one selectedfrom the group consisting of nitrate, sulfate, chlorate, perchlorate,chlorine, and peroxide, and a polishing accelerator.

In example embodiments, during the polishing process on the SOH organiclayer, the polishing accelerator of the slurry compound may be adsorbedon top surfaces of the metal lines.

In example embodiments, the polishing particle may include colloidalceria (CeO₂) particles.

In example embodiments, the polishing particle may have a size rangingfrom about 30 nm to about 80 nm.

In example embodiments, the oxidizing agent may be contained in theslurry compound to have a content ranging from about 0.2 wt % to about0.7 wt % with respect to a total weight of the slurry compound.

In example embodiments, the oxidizing agent may include at least one ofhydrogen peroxide, ammonium perchlorate, sodium chlorate, sodiumchlorite, or ferric nitrate.

In example embodiments, the polishing accelerator may include at leastone amino acid selected from the group consisting of histidine, glycine,glutamine, leucine, methionine, phenylalanine, tryptophan, and valine.

In example embodiments, the polishing accelerator may include at leastone selected from the group consisting of imidazole, imidazolium,chloride, pyridine, tetrazoles, histamine, 1,3-dimethylxanthine,6-mercaptopurine, 1H-1,2,3-triazole, 1H-1,2,4-triazole,poly-[2,2′-(m-phenylen)-5,5′-bisbenzimidazole], 1H-Pyrrole, 1,3-oxazole,1,3-thiazole, Pyrazole, 1-Methylimidazole, and 4-Methyl-1H-imidazole.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments will be more clearly understood from the followingbrief description taken in conjunction with the accompanying drawings.The accompanying drawings represent non-limiting, example embodiments asdescribed herein.

FIG. 1 is a sectional view schematically illustrating a chemicalmechanical polishing apparatus.

FIGS. 2A through 2H are sectional views illustrating a method offabricating a semiconductor device according to example embodiments ofthe inventive concept.

FIG. 3 is a graph showing a polishing rate of an SOH organic layer and amean size of aggregated polishing particles, when a concentration offerric nitrate (FeNO₃) was changed in the slurry compound.

FIG. 4 is a graph showing polishing rates of an SOH organic layer and acopper line, when imidazole-containing and imidazole-free slurrycompounds were used to polish the SOH organic layer and the copper lineformed on a substrate.

FIG. 5A is an image taken from a polished surface of a copper line, whena conventional (i.e., polishing-accelerator-free) slurry compound wasused to polish an SOH organic layer.

FIG. 5B is an image taken from a polished surface of a copper line, whena slurry compound including imidazole as a polishing accelerator wasused to polish an SOH organic layer.

It should be noted that these figures are intended to illustrate thegeneral characteristics of methods, structure and/or materials utilizedin certain example embodiments and to supplement the written descriptionprovided below. These drawings should not be interpreted as defining orlimiting the range of values or properties encompassed by exampleembodiments.

DETAILED DESCRIPTION

Example embodiments of the inventive concept will now be described morefully with reference to the accompanying drawings, in which exampleembodiments are shown. Example embodiments of the inventive concept may,however, be embodied in many different forms and should not be construedas being limited to the embodiments set forth herein; rather, theseembodiments are provided so that this disclosure will be thorough andcomplete, and will fully convey the concept of example embodiments tothose of ordinary skill in the art. In the drawings, the thicknesses oflayers and regions are exaggerated for clarity. Like reference numeralsin the drawings denote like elements, and thus their description will beomitted.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. Like numbers indicate like elementsthroughout. As used herein the term “and/or” includes any and allcombinations of one or more of the associated listed items. Other wordsused to describe the relationship between elements or layers should beinterpreted in a like fashion (e.g., “between” versus “directlybetween,” “adjacent” versus “directly adjacent,” “on” versus “directlyon”).

It will be understood that, although the terms “first”, “second”, etc.may be used herein to describe various elements, components, regions,layers and/or sections, these elements, components, regions, layersand/or sections should not be limited by these terms. These terms areonly used to distinguish one element, component, region, layer orsection from another element, component, region, layer or section. Thus,a first element, component, region, layer or section discussed belowcould be termed a second element, component, region, layer or sectionwithout departing from the teachings of example embodiments.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises”, “comprising”, “includes” and/or “including,” if usedherein, specify the presence of stated features, integers, steps,operations, elements and/or components, but do not preclude the presenceor addition of one or more other features, integers, steps, operations,elements, components and/or groups thereof.

Example embodiments of the inventive concept are described herein withreference to cross-sectional illustrations that are schematicillustrations of idealized embodiments (and intermediate structures) ofexample embodiments. As such, variations from the shapes of theillustrations as a result, for example, of manufacturing techniquesand/or tolerances, are to be expected. Thus, example embodiments of theinventive concept should not be construed as limited to the particularshapes of regions illustrated herein but are to include deviations inshapes that result, for example, from manufacturing. For example, animplanted region illustrated as a rectangle may have rounded or curvedfeatures and/or a gradient of implant concentration at its edges ratherthan a binary change from implanted to non-implanted region. Likewise, aburied region formed by implantation may result in some implantation inthe region between the buried region and the surface through which theimplantation takes place. Thus, the regions illustrated in the figuresare schematic in nature and their shapes are not intended to illustratethe actual shape of a region of a device and are not intended to limitthe scope of example embodiments.

Devices and methods of forming devices according to various embodimentsdescribed herein may be embodied in microelectronic devices such asintegrated circuits, wherein a plurality of devices according to variousembodiments described herein are integrated in the same microelectronicdevice. Accordingly, the cross-sectional view(s) illustrated herein maybe replicated in two different directions, which need not be orthogonal,in the microelectronic device. Thus, a plan view of the microelectronicdevice that embodies devices according to various embodiments describedherein may include a plurality of the devices in an array and/or in atwo-dimensional pattern that is based on the functionality of themicroelectronic device.

The devices according to various embodiments described herein may beinterspersed among other devices depending on the functionality of themicroelectronic device. Moreover, microelectronic devices according tovarious embodiments described herein may be replicated in a thirddirection that may be orthogonal to the two different directions, toprovide three-dimensional integrated circuits.

Accordingly, the cross-sectional view(s) illustrated herein providesupport for a plurality of devices according to various embodimentsdescribed herein that extend along two different directions in a planview and/or in three different directions in a perspective view. Forexample, when a single active region is illustrated in a cross-sectionalview of a device/structure, the device/structure may include a pluralityof active regions and transistor structures (or memory cell structures,gate structures, etc., as appropriate to the case) thereon, as would beillustrated by a plan view of the device/structure.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which example embodiments of theinventive concepts belong. It will be further understood that terms,such as those defined in commonly-used dictionaries, should beinterpreted as having a meaning that is consistent with their meaning inthe context of the relevant art and will not be interpreted in anidealized or overly formal sense unless expressly so defined herein.

[Slurry Compound]

A slurry compound according to example embodiments of the inventiveconcept may have a higher polishing rate on spin-on-hardmask (SOH)organic materials, compared with that of a metal or a nitride. Forexample, in the case where a copper-containing metal layer and anorganic SOH containing layer are polished along with each other, theusage of the slurry compound may make it possible to suppress thecopper-containing metal layer from being polished. Alternatively, in thecase where a silicon nitride layer and an organic SOH containing layerare polished along with each other, the usage of the slurry compound maymake it possible to suppress the silicon nitride layer from beingpolished.

According to example embodiments of the inventive concept, the slurrycompound may include polishing particles, an oxidizing agent, and apolishing accelerator.

The polishing particle may include a material having a higher polishingrate on the SOH organic material than those on a metal or a siliconnitride. The polishing particle may include at least one of silica(SiO₂), ceria (CeO₂), or alumina (Al₂O₃). Further, the polishingparticle may be provided in a colloidal, fumed, or calcination shape.The polishing particle may have a size ranging from about 30 nm to about80 nm. In the case where the size of the polishing particle is less than30 nm, there is generally difficulty in performing mechanical polishingeffectively, whereas in the case where the size of the polishingparticle is greater than 80 nm, the SOH organic material may be damagedduring the polishing process.

The oxidizing agent may oxidize a polymer contained in the SOH organicmaterial and enhance hydrophilicity of the SOH organic material. Theoxidizing agent may include a material having dispersion stability forthe polishing particle and a high polishing rate for the SOH organicmaterial.

The oxidizing agent may include at least one selected from the groupconsisting of nitrate, sulfate, chlorate, perchlorate, chlorine, andperoxide. For example, the oxidizing agent may include at least one ofhydrogen peroxide, ammonium perchlorate, sodium chlorate, sodiumchlorite, and ferric nitrate. The oxidizing agent may be contained inthe slurry compound to have a content ranging from about 0.2 wt % toabout 0.7 wt % with respect to a total weight of the slurry compound. Inthe case where the content of the oxidizing agent is less than about 0.2wt %, it may be more difficult to polish an SOH organic material withefficiency, whereas in the case where the content of the oxidizing agentis higher than about 0.7 wt %, dispersion stability between theoxidizing agent and the polishing particle may be deteriorated.

The polishing accelerator may be selected to preserve a highly activatedstate of the oxidizing agent and thereby polish the SOH organic materialwith a higher polishing rate. Further, the polishing accelerator mayhave a metal-corrosion inhibiting property and/or a metal passivatingproperty. For example, the polishing accelerator may be adsorbed on asurface of a metal layer, thereby protecting the metal layer from metalcorrosion and allowing the SOH organic material to be polished with ahigh polishing selectivity with respect to the metal layer. Thepolishing accelerator may include at least one amino acid selected fromthe group consisting of histidine, glycine, glutamine, leucine,methionine, phenylalanine, tryptophan, and valine. For example, thepolishing accelerator may include at least one selected from the groupconsisting of imidazole, imidazolium, chloride, pyridine, tetrazoles,histamine, 1,3-dimethylxanthine, 6-mercaptopurine, 1H-1,2,3-triazole,1H-1,2,4-triazole, poly-[2,2′-(m-phenylen)-5,5′-bisbenzimidazole],1H-Pyrrole, 1,3-oxazole, 1,3-thiazole, pyrazole, 1-Methylimidazole, and4-Methyl-1H-imidazole.

By using the nitrate-based oxidizing agent in the slurry compound, it ispossible to polish an SOH organic material, which is generally notsufficiently polished by an oxidizing-agent-free slurry compound.Further, by using a slurry compound containing a polishing accelerator(e.g., imidazole), it is possible to improve a polishing selectivitybetween the SOH organic material and the metal or nitride layer.

[Chemical Mechanical Polishing Apparatus]

FIG. 1 is a sectional view schematically illustrating a chemicalmechanical polishing apparatus.

Referring to FIG. 1, a chemical mechanical polishing apparatus 100 mayinclude a rotation table 110 attached with a polishing pad 112, apolishing head 130 facing the rotation table 110, a slurry supplyingpart 140 provided adjacent to the polishing pad 112, and a polishing padconditioner (not shown).

The rotation table 110 may be shaped like a circular disk, and a firstdriving part 114 may be connected to a bottom of the rotation table 110to provide a rotating force to the rotation table 110. The polishing pad112 may be attached on a top surface of the rotation table 110 to polisha to-be-polished surface.

A plurality of pores (not shown) may be formed on a surface of thepolishing pad 112. If a slurry compound 142 is supplied during achemical mechanical polishing (CMP) process on the to-be-polishedsurface, it may be stored in the pores of the polishing pad 112.

The polishing head 130 may hold a wafer W in such a way that theto-be-polished surface of the wafer W faces the rotation table 110.During the CMP process on the wafer W, the polishing head 130 may bepressed in contact with the to-be-polished surface to the polishing pad112, and the polishing head 130 may be coupled with a second drivingpart 120 for rotating the wafer W. The polishing head 130 and therotation table 110 may have different rotating directions from eachother. Alternatively, the polishing head 130 and the rotation table 110may have the same rotating direction as each other.

Although not shown in detail, an air housing may be formed in thepolishing head 130 to hold the wafer W and press the to-be-polishedsurface of the wafer W onto the polishing pad 112. The air housing maybe expanded or contracted to hold the wafer W, and the to-be-polishedsurface of the wafer W may be pressed onto the polishing pad 112 usingthe air housing. A retainer ring 132 may be provided on a bottom rimportion of the polishing head 130 to fasten the wafer W. The retainerring 132 and the wafer W may be in contact with the polishing pad 112,during the CMP process on the wafer W.

The slurry supplying part 140 may supply the slurry compound 142 ontothe polishing pad 112. The slurry compound 142 may include the polishingparticle, the oxidizing agent, and the polishing accelerator asdescribed above, and therefore, for brevity's sake, a detail descriptionthereof will be omitted.

The polishing pad conditioner may be disposed on the polishing pad 112and be configured to spray a pressurized vapor onto a surface of thepolishing pad 112, thereby improving a surface state of the polishingpad 112.

The following is an example of a CMP process, in which the chemicalmechanical polishing apparatus 100 is used to planarize a to-be-polishedsurface of a wafer W.

The polishing head 130 may hold the wafer W in such a way that theto-be-polished surface of the wafer W faces the polishing pad 112. Inexample embodiments, the to-be-polished surface may include an SOHorganic material. In certain embodiments, the wafer W may furtherinclude a metal or a nitride.

The wafer W may be pressed in contact with a rotating top surface of thepolishing pad 112. Here, the slurry compound 142 may be supplied fromthe slurry supplying part 140 onto the polishing head 130. In exampleembodiments, the slurry compound 142 may be prepared to realize a higherpolishing rate of the SOH organic material with respect to a metal or anitride. The slurry compound 142 may contain the afore-describedmaterial for the slurry compound 142, and for brevity's sake, a detaildescription thereof will be omitted.

The slurry compound 142 stored in the pores of the polishing pad 112 andthe rotation of the polishing pad 112 may allow the wafer W to bepolished chemically and mechanically. By-products may be produced by thepolishing of the wafer W, and a mixture of the by-products and theslurry compound 142 may clog the pores of the polishing pad 112.

The mixture of the by-products and the slurry compound 142 may beremoved from the pores by the conditioner supplied from the polishingpad conditioner and then may be removed from the polishing pad 112 bythe rotation of the polishing pad 112.

[Method of Fabricating a Semiconductor Device]

FIGS. 2A through 2H are sectional views illustrating a method offabricating a semiconductor device according to example embodiments ofthe inventive concept.

Referring to FIG. 2A, an insulating layer 210 may be formed on a lowerstructure 200. The insulating layer 210 may include an oxide, a nitride,and/or an oxynitride. In the present embodiment, the insulating layer210 may be formed of or include a silicon oxide layer.

Although not shown in detail, the lower structure 200 may include aswitching device (e.g., a transistor or a diode) or an interconnectionstructure (e.g., bit lines).

Referring to FIG. 2B, metal lines 220 may be formed on the insulatinglayer 210. Each of the metal lines 220 may extend in a direction and mayinclude at least one of copper (Cu), aluminum (Al), or tungsten (W).

In example embodiments, the metal lines 220 may be formed by formingsacrificial patterns (not shown) on the insulating layer 210, formingthe metal lines 220 to fill gap regions between the sacrificialpatterns, and removing the sacrificial patterns.

In other example embodiments, the metal lines 220 may be formed byforming a metal layer (not shown) on the insulating layer 210, forming amask (not shown) on the metal layer, and etching the metal layer usingthe mask as an etch mask.

Referring to FIG. 2C, an SOH organic layer 230 may be formed on themetal lines 220 to fill gap regions between the metal lines 220. Inexample embodiments, the SOH organic layer 230 may be formed to whollycover the metal lines 220 and have a top surface higher than those ofthe metal lines 220.

In the case where a general slurry compound is used to polish the SOHorganic layer 230, the SOH organic layer 230 may be damaged.

In certain embodiments, as shown in FIG. 2D, a nitride layer 225 may befurther formed between the metal lines 220 and the SOH organic layer 230to prevent a native oxide from being formed on the metal lines 220. Forexample, the nitride layer 225 may be a silicon nitride layer.

Referring to FIG. 2E, the SOH organic layer 230 may be polished toexpose top surfaces of the metal lines 220, and thus, SOH patterns 240may be formed between the metal lines 220.

In example embodiments, the polishing of the SOH organic layer 230 maybe performed by a chemical-mechanical polishing process, in which theslurry compound according to example embodiments of the inventiveconcept is used. The slurry compound may be selected to allow the SOHorganic layer 230 containing the SOH organic material to have apolishing rate different from those of the metal lines 220. For example,when the SOH organic layer 230 is polished, the metal lines 220 may havean extremely low polishing rate and may serve as a polishing-stoppinglayer.

The slurry compound according to example embodiments of the inventiveconcept may include the polishing particle, the oxidizing agent, and thepolishing accelerator previously described.

In the case where the nitride layer 225 is additionally formed betweenthe metal lines 220 and the SOH organic layer 230, the slurry compoundmay be selected to allow the SOH organic layer 230 containing the SOHorganic material to have a polishing rate different from that of thenitride layer 225. For example, when the SOH organic layer 230 ispolished, the nitride layer 225 may have an extremely low polishing rateand may serve as a polishing-stopping layer.

Referring to FIG. 2F, a thin-film 250 may be formed on the metal lines220 and the SOH patterns 240. A material contained in the thin-film 250may be variously changed depending on a subsequent process. In exampleembodiments, the thin-film 250 may include an oxide-based material(e.g., silicon oxide). As an example, the thin-film 250 may be formed ofor include an oxide layer formed by a rapid-thermalatomic-layer-deposition (RT ALD) process.

Referring to FIG. 2G, the SOH patterns 240 may be selectively removed.In example embodiments, the SOH patterns 240 may be removed using anoxygen (O₂) ashing process. As a result of the removal process, air gaps260 may be formed between two adjacent ones of the metal lines 220 andmay be veiled by the thin-film 250. The metal lines 220 may beelectrically separated from each other by the air gaps 260.

As described above, by forming the metal lines 220 and removing the SOHpatterns 240 between the metal lines 220, the air gaps 260 can be formedto have a uniform size. In addition, by forming the thin-film 250 beforethe removal of the SOH patterns 240, it is possible to easily perform asubsequent process of forming upper structures 270.

Referring to FIG. 2H, an upper structure 270 may be formed on thethin-film 250. In the case where the thin-film 250 contains oxide, theupper structure 270 may include an oxide layer.

Experimental Example To Select Polishing Particle

The present experiment was performed to select a polishing particle fora slurry compound. In the present experiment, ceria and silica were usedas the polishing particles, since they have a different polishing ratecompared to an SOH organic layer and a nitride layer. As describedabove, a nitride layer was formed on metal lines to suppress a nativeoxide from being formed on the metal lines.

Table 1 shows polishing rates of SOH and SiN layers and an extent of asurface scratch of the SOH organic layer, according to types, shapes,and sizes of materials, which can be used as the polishing particle.

TABLE 1 SOH SiN Polishing Size polishing rate polishing rate ParticleShape [nm] [Å/min] [Å/min] Scratch ceria calcination 250 3,500 105 310ceria calcination 100 2,700 60 260 ceria colloid 60 1,300 20 20 ceriacolloid 30 1,260 18 15 silica fumed 100 3,000 350 32 silica colloid 302,200 270 13

As shown in Table 1, the polishing rate of SiN layer was less than thepolishing rate for ceria particles than for silica particles. Comparedwith the use of the calcination-type of ceria particle, the surfacescratch of the SOH organic layer was reduced when the colloid-type ofceria particle was used. This shows that the colloid-type of ceriaparticle is more suitable as the polishing particle.

To Select Oxidizing Agent

The present experiment was performed to select an oxidizing agentsuitable for the slurry compound for polishing an SOH organic layer,when the colloid-type of ceria particle was selected as the polishingparticle. Table 2 shows polishing rate and dispersion stability of theSOH organic layer, when some materials for the oxidizing agent weremixed in a slurry compound.

TABLE 2 Oxidizing SOH Polishing Rate Dispersion Agent [Å/min] StabilityRemark sulfate 700 Normal chlorate 860 Aggregation perchlorate 760Aggregation chlorine 710 Aggregation nitrate 1,200 Normal peroxide 210Aggregation Change of color

As shown in Table 2, sulfate and nitrate had better properties indispersion stability to the polishing particle, when they were containedin the slurry compound. In particular, the polishing rate of the SOHorganic layer was higher when the oxidizing agent of nitrate was usedthan when the oxidizing agent of sulfate was used, and thus, nitrate wasselected as the oxidizing agent.

Table 3 and FIG. 3 show a polishing rate of an SOH organic layer and amean size of aggregated polishing particles, when a concentration offerric nitrate (FeNO₃) serving as the nitrate for the oxidizing agentwas changed in the slurry compound.

TABLE 3 FeNO₃ SOH Polishing Rate Mean Size [wt %] [Å/min] [nm] 0.00 0 600.15 250 62 0.10 560 60 0.15 780 60 0.20 970 60 0.40 1,080 60 0.60 1,20060 0.70 1,150 65 0.80 1,130 105 1.00 1,160 143

As shown in Table 3 and FIG. 3, the higher the concentration of theferric nitrate, the higher the polishing rate of the SOH organic layer.However, if the ferric nitrate of 0.80 wt % or higher was used, the meansize of the aggregated polishing particles was increased, and from this,it was preferable that the oxidizing agent in the slurry compound have aconcentration ranging from about 0.2 wt % to about 0.7 wt %.

To Select Polishing Accelerator

The present experiment was performed to select a polishing acceleratorfor a slurry compound. Table 4 shows polishing rates of an SOH organiclayer and a copper line, when some materials for the polishingaccelerator were contained in a slurry compound to have a concentrationof 0.2 wt %.

TABLE 4 Compound Polishing Rate [Å/min] (0.2 wt %) SOH Cu Remarkcarboxylic acid 470 210 Aggregation histidine 2,700 330 glycine 2,650310 imidazole 2,810 28 formic acid 1,230 295 inorganic acid 120 105

As shown in Table 4, when histidine, glycine, and imidazole were used asthe polishing accelerator, the SOH organic layer had a polishing rate of2,500 Å/min or higher. However, when histidine and glycine were used,the copper line had a polishing rate of 300 Å/min or higher, whereaswhen imidazole was used, the copper line had a very low polishing rateof 28 Å/min. This shows that an azole-based material is suitable for thepolishing accelerator.

FIG. 4 is a graph showing polishing rates of an SOH organic layer and acopper line, when imidazole-containing and imidazole-free slurrycompounds were used to polish the SOH organic layer and the copper lineformed on a substrate.

Referring to FIG. 4, in the case that the imidazole-free slurry compoundwas used to polish an SOH organic layer formed on a copper line, the SOHorganic layer had a polishing rate of about 1,230 Å/min and the copperline had a polishing rate of about 730 Å/min. That is, a polishingselectivity therebetween was very low, about 1.68.

By contrast, in the case that the imidazole-containing slurry compoundwas used to polish an SOH organic layer formed on a copper line, the SOHorganic layer had a polishing rate of about 2,840 Å/min and the copperline had a polishing rate of about 23 Å/min. That is, a polishingselectivity therebetween was remarkably increased to about 123.5.

FIGS. 5A and 5B are images taken from polished surfaces of copper lines,after a polishing process. The image of FIG. 5A was taken from apolishing process, in which a conventional (i.e.,polishing-accelerator-free) slurry compound was used to polish an SOHorganic layer, and the image of FIG. 5B was taken from another polishingprocess, in which the slurry compound according to example embodiments(i.e., including imidazole as a polishing accelerator) was used.

According to the present embodiment, in the case where the polishingaccelerator such as imidazole is used, it is possible to increase apolishing rate of an SOH organic layer, and imidazole may be adsorbed ona surface of a metal layer (e.g., of copper), thereby protecting thesurface of the metal layer against the polishing process.

The surface shown in FIG. 5B exhibited an improved corrosion property,compared to that shown in FIG. 5A. When the imidazole or the polishingaccelerator is contained in the slurry compound, the presence of theimidazole adsorbed on surfaces of the copper lines led to moredifficulty in making contact between the oxidizing agent and thesurfaces of the copper lines, leading to a reduction in corrosion of thecopper line, as shown in FIG. 5B.

According to example embodiments of the inventive concept, a slurrycompound may be prepared to include an oxidizing agent containing atleast one selected from the group consisting of nitrate, sulfate,chlorate, perchlorate, chlorine, and peroxide, and the use of the slurrycompound may make it possible to polish an SOH organic layer withefficiency. Further, the slurry compound may contain a polishingaccelerator, allowing the SOH organic layer to be polished with a highpolishing selectivity with respect to metal lines.

While example embodiments of the inventive concept have beenparticularly shown and described, it will be understood by one ofordinary skill in the art that variations in form and detail may be madetherein without departing from the spirit and scope of the attachedclaims.

What is claimed is:
 1. A slurry compound comprising: a polishingparticle; an oxidizing agent comprising at least one selected from thegroup consisting of a nitrate, a sulfate, a chlorate, a perchlorate, achlorine, and a peroxide; and a polishing accelerator.
 2. The slurrycompound of claim 1, wherein the polishing particle comprises colloidalceria (CeO₂) particles.
 3. The slurry compound of claim 1, wherein thepolishing particle has a size in a range from about 30 nm to about 80nm.
 4. The slurry compound of claim 1, wherein the oxidizing agent ispresent in an amount in a range from about 0.2 wt % to about 0.7 wt %with respect to a total weight of the slurry compound.
 5. The slurrycompound of claim 1, wherein the oxidizing agent comprises at least oneof hydrogen peroxide, ammonium perchlorate, sodium chlorate, sodiumchlorite, and ferric nitrate.
 6. The slurry compound of claim 1, whereinthe polishing accelerator is adsorbed on a surface of a metal.
 7. Theslurry compound of claim 1, wherein the polishing accelerator comprisesat least one amino acid selected from the group consisting of histidine,glycine, glutamine, leucine, methionine, phenylalanine, tryptophan, andvaline.
 8. The slurry compound of claim 1, wherein the polishingaccelerator comprises at least one selected from the group consisting ofimidazole, imidazolium, chloride, pyridine, tetrazoles, histamine,1,3-dimethylxanthine, 6-mercaptopurine, 1H-1,2,3-triazole,1H-1,2,4-triazole, poly-[2,2′-(m-phenylen)-5,5′-bisbenzimidazole],1H-pyrrole, 1,3-oxazole, 1,3-thiazole, pyrazole, 1-methylimidazole, and4-methyl-1H-imidazole.
 9. A method of fabricating a semiconductordevice, comprising: forming metal lines on a substrate; forming an SOHorganic layer on the metal lines to fill gaps between the metal lines;performing a polishing process on the SOH organic layer to expose a topsurface of the metal lines and form SOH organic patterns between themetal lines; forming a thin film on the metal lines and the SOH organicpatterns; and selectively removing the SOH organic patterns to form airgaps between the metal lines, wherein the polishing process is performedusing a slurry compound comprising (a) a polishing particle, (b) anoxidizing agent containing at least one selected from the groupconsisting of a nitrate, a sulfate, a chlorate, a perchlorate, achlorine, and a peroxide, and (c) a polishing accelerator.
 10. Themethod of claim 9, wherein, during the polishing process on the SOHorganic layer, the polishing accelerator of the slurry compound isadsorbed on a top surface of the metal lines.
 11. The method of claim 9,wherein the polishing particle comprises colloidal ceria (CeO₂)particles.
 12. The method of claim 9, wherein the polishing particle hasa size in a range from about 30 nm to about 80 nm.
 13. The method ofclaim 9, wherein the oxidizing agent is present in an amount in a rangefrom about 0.2 wt % to about 0.7 wt % with respect to a total weight ofthe slurry compound.
 14. The method of claim 9, wherein the oxidizingagent comprises at least one of hydrogen peroxide, ammonium perchlorate,sodium chlorate, sodium chlorite, or ferric nitrate.
 15. The method ofclaim 9, wherein the polishing accelerator comprises at least one aminoacid selected from the group consisting of histidine, glycine,glutamine, leucine, methionine, phenylalanine, tryptophan, and valine.16. The method of claim 9, wherein the polishing accelerator comprisesat least one selected from the group consisting of imidazole,imidazolium, chloride, pyridine, tetrazoles, histamine,1,3-dimethylxanthine, 6-mercaptopurine, 1H-1,2,3-triazole,1H-1,2,4-triazole, poly-[2,2′-(m-phenylen)-5,5′-bisbenzimidazole],1H-pyrrole, 1,3-oxazole, 1,3-thiazole, pyrazole, 1-methylimidazole, and4-methyl-1H-imidazole.
 17. A slurry compound comprising: a colloid-typeceria (CeO₂) particle; a nitrate oxidizing agent; and an azole polishingaccelerator.
 18. The slurry compound of claim 17, wherein the nitrateoxidizing agent is ferric nitrate (FeNO₃).
 19. The slurry compound ofclaim 17, wherein the azole polishing accelerator is imidazole.
 20. Theslurry compound of claim 17, wherein the nitrate oxidizing agent ispresent in an amount from about 0.2 wt % to about 0.7 wt % with respectto a total weight of the slurry compound.